This work focuses on magnetic resonance studies of the nature of catalysis by serine proteases, the allosteric cooperativity of hemoglobin ligation, the negative cooperativity or "half-of-the-sites" reactivity of glyceraldehyde-3-phosphate dehydrogenase, binding of antigen to antibodies and the nature of subsequent changes that initiate the complement cascade, the interaction of cholinergic ligands with the acetylcholine receptor of Torpedo californica and the mechanisms by which a sperm penetrates and ovum during fertilization. BIBLIOGRAPHIC REFERENCES: Mechanism of Serine Protease Action. Ionization Behavior of Tetrahedral Adduct Between Alpha-Lytic Protease and Tripeptide Aldehyde Studied by 13C Magnetic Resonance, Michael W. Hunkapiller, Stephen H. Smallcombe and John H. Richards, Org. Magnetic Resonance, 7, 262 (1975). 19F Nuclear Magnetic Resonance Studies of Structure and Function Relationships in Trifluoracetonylated Rabbit Muscle Glyceraldehyde-3-Phosphate Dehydrogenase, J. Bode, M. Blumenstein and M. A. Raftery, Biochemistry, 14, 1153 (1975).